igh altitude interceptor variant of the
Yak-1. Its major difference from other
sibblings - M-106 engine, which was designed
at Mikulin KB under Governmental Order issued on January 9,
1941.

M-106 (also known as M-106-1sk) was a
M-105PF variation. Major distinction -
single-speed centrifugal supercharger, providing intake pressure 1175mm.Hg. As a
result, engine gained up to 150hp of output. The supercharger was designed by
V.A.Dollezhal.

Single-speed supercharger allowed to eliminate a power drop at 1850m, where
M-105PF supercharger had a speed change.
Elemination of this power drop (known to and exploited by Luftvaffe pilots) could provide
Soviet pilots with certain advantage at low and medium altitudes, where most of dogfight
took place.

Airframe modifications were minor weight saving changes and installation of the VISh-61P
variable-pitch propeller. Yak-1 M-106 had fuselage of series
Yak-1 (which one? - A.S.),
metal tail stabiliser and rudder from Yak-7,
metal wing spars, two
wing fuel takns. Oil coolers (9' diameter) were installed in wing tunnels. Tunnel of the water
cooler was modified according to recent TsAGI
recomendations.

Yak-1 M-106 was armed with engine-mounted 20mm ShVAK and 12.7mm UBS guns.
Other equipment was identical to series Yak-1 M-105PF.

Engine progressed slowly, and only on December 12, 1942
assembly of test fighter was ordered by GKO.
Yak-1 M-106 was assembled in end of December, 1942. In
January 1943 trials were undertaken by test-pilot
A.I.Kokin, seniour engineer K.N.Mkrtychan and aircraft mechanic F.Z.Sbitnev.

Flight performance obteined during factory trials was substantially better than of series
Yak-1 M-105PF. But... those advantages could not be
obtained at air temperatures above 15°C. Cooling system productivity, despite was increased
compared to standard M-105PF, could not coup with
increased engine heat outpup on maximum climb rate.

Factory trials revealed also that the engine needs more work on it. Vibration on transitional (1800 to
2000rpm) rates, frequent spark plug failures, smoke, excessive fuel consumption and 'diseling'
required serious attention of engine designers. It was transferred to
LII.

Also in January (8 to 13) 1943 another Yak-1
with M-106 engine was tested at
LII. This was a seruies
Yak-1 M-105PF with standard airframe. It had lower assembly
quality and was heavier than specially-built modified stblemate. Performance worsened, and engine
had same toothing problems.

Monetheless, production of the Yak-1 M-106 was launched. 47 aircraft were assembeld at Saratov until
February 18, 1943. 32 of them had standard cooling system
and were designated for winter conditions combat trials. But this was the end of the story. None of those
machines saw action, because all were rejected by military representatives. Temperature regimes were found
not acceptable, M-106 engines were graded as unsuitable and
replaced by standard M-105PF.